The present invention relates to systems and methods for controlling the operation of multi-stage air conditioners. More particularly, the invention relates to such a system and method that achieves better temperature and humidity control and substantial energy savings.
Buildings and other areas with high internal heat loads, such as telecommunications equipment buildings, require cooling throughout the year even when outside temperatures are cold. Conventional residential and commercial air conditioners cannot be used for these applications because they are not designed for operation when outside temperatures are below 60° F. (15° C.). Therefore, air conditioning units that are engineered specifically for such applications with necessary controls, features, and safeties are required.
Telecommunications equipment buildings and other remote sites also typically require two or more redundant air conditioning units to provide necessary cooling in case one of the air conditioning units malfunctions. A thermostat controller may be used to operate the air conditioners in a lead/lag manner, where the start-up of the air conditioners is alternated so that both air conditioners experience approximately the same run-time over their lives.
To better match the cooling requirements of a building or other area with the operating performance of its air conditioning units, many newer high efficiency air conditioners are available with two-stage compressors. Such air conditioners may have, for example, a first stage that is 65% of the total compressor capacity, and a second stage that is 100% of the compressor capacity. When operating in their first stages, the air conditioners are approximately 20% more efficient than when operating in their second stages. Unfortunately, existing thermostat controllers do not properly control the operation of such high efficiency air conditioners to achieve maximum energy savings.